The present invention relates to a recording medium conveying device, particularly to a recording medium conveying device which conveys a recording medium in accordance with image recording.
An image recording apparatus such as an ink jet printer is equipped with a recording medium conveying device which conveys a recording medium in accordance with image recording (see the Patent Documents 1 and 2, for examples.) The recording medium conveying device has a master roll holding section that holds the master roll of the recording medium upstream of the platen which is positioned in an image recording area of the image recording apparatus, and it also has an ejecting section that ejects the recording medium after recording an image downstream of the platen.
If the recording medium is lifted in this operation, the distance between the recording head and the recording medium becomes non-uniform, resulting in image quality degradation. Accordingly, the recording medium conveying device conveys the recording medium along the platen so as to maintain flatness.
[Patent Document 1] Tokkai No. 2000-326572
[Patent Document 2] Tokkai No. 2003-137464
However, an ink jet printer may record images on various different kinds of recording media and, because the stiffness of a recording medium is different from type to type, the recording medium may be lifted on the platen depending on its stiffness.
For example, a recording medium with high stiffness can be conveyed smoothly without being in tension because of its high stiffness, but a recording medium with low stiffness cannot be conveyed at a stable feed rate if no tension is added to the medium. Accordingly, if the conveyance path is so designed that the recording medium is tilted upward in the traveling direction when it enters the platen, tension is added by the weight of the recording medium itself. However, if a recording medium with high stiffness is conveyed on this conveyance path, there is a possibility that the recording medium is lifted from the platen because of its stiffness when it transfers from the tilted portion onto the platen. On the other hand, when the recording medium is ejected after having an image recorded, a recording medium with high stiffness can be ejected smoothly without added tension because of its high stiffness. In case of ejecting a recording medium with low stiffness, however, if no tension is added, buckling may be caused by the conveyance resistance to the recording medium when it is separated from the platen. This buckling may cause the recording medium to rub against the discharge surface of the recording head, possibly resulting in recording medium jamming.
If the conveyance path is so designed that the recording medium is tilted downward in the traveling direction when the recording medium separates from the platen, tension is added by the weight of the recording medium itself. However, if a recording medium with high stiffness is conveyed on this conveyance path, the recording medium may be lifted from the platen because of its form maintaining force due to the stiffness when the recording medium hangs down, and may rub against the discharge surface of the recording head, possibly resulting in recording medium jamming.